This proposal seeks to interview residents of 13 counties of western Washington who were diagnosed as having testicular cancer during 1978-82, in order to deter the proportion in whom a vasectomy had been performed prior to diagnosis. For purposes of comparison, identical interviews will be obtained from a random sample of men from the same population. The results of this comparison should provide an insight into what, if any, role vasectomy plays in the etiology of testicular cancer.